The present invention relates to a work vehicle having a fluid pressure circuit system for a backhoe structure and the like which comprises a vertically oscillatable arm mounted on a swivel deck and a flection arm connected to the tip end of the oscillatable arm and carrying an oscillatable bucket. More particularly, the invention is directed to a work vehicle having a fluid pressure circuit system that is arranged to cause the swivelling of a work equipment, such as an arm assembly on a vertical axis with the pump means for the vertical oscillation or reflection of the arm.
In the case of using a common pump means to supply fluid pressure both for the vertical oscillation or reflection of the work equipment and for the swivelling of the work equipment as above described, the pump means needs to have a large capacity to actuate the work equipment at high speed. For this reason, when the work equipment is only swivelled, the swivelling speed is unnecessarily high, which brings about a disadvantage of subjecting the work equipment to a great shock at the start and hault of the swivelling.
In order to overcome such a disadvantage, a conventional method employs a throttle valve on the fluid pressure circuit for the swivelling of the work equipment. However, this entails a further problem by causing the relief valve adapted for pressure determination to operate easily, which will result in a rise in the fluid temperature, noises and a great power loss.